Cell culture and cell viability assay

Rat C6 glioma cells (Korean Cell Line Bank, Seoul, Korea) were cultured in DMEM medium (containing 10% fetal bovine serum (FBS) and 1% penicillin-streptomycin) at 37℃, humidified with 5% atmospheric CO₂. Cell viability analyses were performed as previously reported [25]. Briefly, C6 glioma cells (5 × 10³ cells/well) were seeded and incubated in a 96-well micro-plate for 24 h. The cells were replaced with serum-free medium and incubated for the next 24 h. Subsequently, the cells were treated with different concentrations of CK (0.03 µM to 10 µM dissolved in 0.05% DMSO and diluted in serum-free medium), followed by re-incubation for another 24 h. Cell viability was measured using an EZ-cytox cell viability assay kit. Absorbance was determined using ELISA at a wavelength of 450 nm. Each assay was performed in triplicate.